# Derivation of color from light **URL:** \ **Category:** Factual Questions\ **Created:** [August 29, 2003, 6:25pm UTC](https://boards.straightdope.com/t/derivation-of-color-from-light/198480 "2003-08-29T18:25:26Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![commasense](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/commasense/32/3017_2.png) [@commasense](https://boards.straightdope.com/u/commasense)\ **Post date:** [August 30, 2003, 2:17am UTC](https://boards.straightdope.com/t/derivation-of-color-from-light/198480/21 "2003-08-30T02:17:36Z")
Sorry, **Q.E.D.** (and I realize that this is veering perilously near GD territory), but it’s simply playing games with language to claim that color and flavor don’t exist. If you’re going to insist that color exists only in the brain you might as well say that _everything_ exists only in the brain. Color is _defined_ as the experience of perceiving light of certain frequencies; flavor is _defined_ as the effect certain compounds have on the taste buds. There is a direct connection between the frequency of light (which you call an “inherent property”) and the perception we call color. Likewise flavors. Hence color and flavor and the universe all exist. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [August 30, 2003, 2:28am UTC](https://boards.straightdope.com/t/derivation-of-color-from-light/198480/22 "2003-08-30T02:28:24Z")
> [@](#): > > \*Originally posted by commasense \* > **Color is _defined_ as the experience of perceiving light of certain frequencies; flavor is _defined_ as the effect certain compounds have on the taste buds.** Yes, and none of that occurs outside of the brain. If you have a continuously varying range of wavelengths of light, on inspection there is no distinct point at which one can say the color has changed. you say color is “defined as the experience of perceiving light of certain frequencies”, and I concur. But the experience of perception occurs _in_ the brain and nowhere else. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [August 30, 2003, 3:19am UTC](https://boards.straightdope.com/t/derivation-of-color-from-light/198480/23 "2003-08-30T03:19:25Z")
> [@](#): > > \*Originally posted by erislover \* > \*\*We have two perspectives, the Relativistic Spaceship travelling quite fast (say, .5c) and the Stationary Observer who obviously isn’t really stationary but whatever. The RS is travelling in a line relative to the sun, and the SO is on earth (travelling mostly pretty slow). All photons leaving our ideal sun have energy e. Since the speed of light is the same for all observers, the RS sees a red-shift in the photons, meaning their wavelength has changed. But photon energy is dependent on wavelength, so the RS is going to measure a different amount of energy than the SO, right? But they’re the same photons. Why is this driving me crazy? \*\* Sounds right to me. Photon energy is like kinetic energy; it’s different for different observers. If a flying seagull bumped into you (a “stationary” observer), it’ll be a fairly gentle collision (small kinetic energy). If the same seagull bumped into the windshield of a flying jet aircraft, it’s going to be a much bigger impact (large kinetic energy). Likewise, a head-on collision with a photon hurts more than a photon hitting you on the ass on your way out. As for the color vs. wavelength vs. frequency, I don’t see why we need to say “color doesn’t exist” for the purpose of this OP. Color corresponds to photon energy, which is proportional to the effective frequency of the photon. When a photon travels through a dense medium, the effective wavelength changes but the energy and effective frequency remains the same. ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [August 30, 2003, 4:19am UTC](https://boards.straightdope.com/t/derivation-of-color-from-light/198480/24 "2003-08-30T04:19:51Z")
If a spectrometer tells me that the light _it’s_ looking at has a wavelength of 500 nm, I don’t need to see the light myself to know that the light corresponds to what is called “green”. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [August 30, 2003, 4:30am UTC](https://boards.straightdope.com/t/derivation-of-color-from-light/198480/25 "2003-08-30T04:30:06Z")
> [@](#): > > \*Originally posted by Desmostylus \* > \*\*If a spectrometer tells me that the light _it’s_ looking at has a wavelength of 500 nm, I don’t need to see the light myself to know that the light corresponds to what is called “green”. \*\* If you’re a completely colorblind individual, are you instinctively going to know what “green” is? No. You can restate the proposition any way you like, but the actual perception of color occurs in the brain, and is not an inherent characteristic of the light itself. If you disagree, tell me, what color is the 2 meter RF band? What colors are gamma rays? ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [August 30, 2003, 4:55am UTC](https://boards.straightdope.com/t/derivation-of-color-from-light/198480/26 "2003-08-30T04:55:04Z")
> [@](#): > > \*Originally posted by Q.E.D. \* > **… actual perception of color occurs in the brain, and is not an inherent characteristic of the light itself.** I think most astronomers would disagree with this. Green is a name given to a wavelength range in the middle of the visible spectrum. A colorblind person can use a spectrometer and a dictionary to find the color of any visible light. If you had no sense of taste and a chemical analysis of an unknown liquid shows it’s NaCl dissolved in water, would it be wrong for you to conclude that it is salty? > [@](#): > > \*\*If you disagree, tell me, what color is the 2 meter RF band? What colors are gamma rays? \*\* The term “color” only refers to visible light. That doesn’t make it an invalid classification scheme. Anyway, why do you feel this distinction is important for this thread? Our eyes perceive different photon energy as different color, so it’s perfectly reasonable to say “color is associated with photon energy.” ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [August 30, 2003, 5:02am UTC](https://boards.straightdope.com/t/derivation-of-color-from-light/198480/27 "2003-08-30T05:02:04Z")
This is ridiculous. It’s like saying sound doesn’t exist because deaf people can’t hear it. The lack of labels for frequencies outside human visual range doesn’t help you out. We don’t really have labels for different sound frequencies, either. What “pitch” is 442 Hz? The term “pitch” just means frequency. You can’t claim that a 25 kHz sound doesn’t have a pitch simply because it’s outside human auditory range. ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [August 30, 2003, 5:08am UTC](https://boards.straightdope.com/t/derivation-of-color-from-light/198480/28 "2003-08-30T05:08:06Z")
This is ridiculous. It’s like saying sound doesn’t exist because deaf people can’t hear it. The lack of labels for frequencies outside human visual range doesn’t help you out. We don’t really have labels for different sound frequencies, either. What “pitch” is 442 Hz? The term “pitch” just means frequency. You can’t claim that a 25 kHz sound doesn’t have a pitch simply because it’s outside human auditory range. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [August 30, 2003, 5:08am UTC](https://boards.straightdope.com/t/derivation-of-color-from-light/198480/29 "2003-08-30T05:08:53Z")
> [@](#): > > \*Originally posted by scr4 \* > **I think most astronomers would disagree with this. Green is a name given to a wavelength range in the middle of the visible spectrum. A colorblind person can use a spectrometer and a dictionary to find the color of any visible light.** You are completely missing the point. Why is the name “green” given to that particular range of wavelengths? Because people who can see those colors say so, that’s why. A colorblind person can read the color name “green” but does he understand what that means? No. Show me an astronomer who thinks color is actually an inherent property of EM radiation. ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [August 30, 2003, 5:13am UTC](https://boards.straightdope.com/t/derivation-of-color-from-light/198480/30 "2003-08-30T05:13:08Z")
Freakin’ hamsters. And my post was obviously a reply to **Q.E.D.** , not **scr4**. Anyway, let’s look at the dictionary: > [@](#): > > **col·or** > _n._ > > 1. That aspect of things that is caused by differing qualities of the light reflected or emitted by them, definable in terms of the observer or of the light, as: > a. The appearance of objects or light sources described in terms of the individual’s perception of them, involving hue, lightness, and saturation for objects and hue, brightness, and saturation for light sources. > b. The characteristics of light by which the individual is made aware of objects or light sources through the receptors of the eye, described in terms of dominant wavelength, luminance, and purity. Note: “definable in terms of the observer **or** of the light” ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [August 30, 2003, 5:17am UTC](https://boards.straightdope.com/t/derivation-of-color-from-light/198480/31 "2003-08-30T05:17:39Z")
> [@](#): > > \*Originally posted by Q.E.D. \* > \*\*Show me an astronomer who thinks color is actually an inherent property of EM radiation. \*\* I hate having to use my background to back up my statements but since you ask, I _am_ an astronomer. I may not have a Ph.D quite yet but I make a living as an astronomy researcher. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [August 30, 2003, 5:22am UTC](https://boards.straightdope.com/t/derivation-of-color-from-light/198480/32 "2003-08-30T05:22:28Z")
> [@](#): > > \*Originally posted by Desmostylus \* > \*\*This is ridiculous. It’s like saying sound doesn’t exist because deaf people can’t hear it. > > The lack of labels for frequencies outside human visual range doesn’t help you out. We don’t really have labels for different sound frequencies, either. What “pitch” is 442 Hz? The term “pitch” just means frequency. You can’t claim that a 25 kHz sound doesn’t have a pitch simply because it’s outside human auditory range. \*\* Being outside our normal range of perception has nothing whatsoever to do with this. Color is NOT the same as wavelength, despite the close relationship. Color is the _perception_ of what a given wavelength looks like to us. Can you prove to me that what we see as “red” doesn’t look like “blue” to some other species, for example. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [August 30, 2003, 5:25am UTC](https://boards.straightdope.com/t/derivation-of-color-from-light/198480/33 "2003-08-30T05:25:36Z")
> [@](#): > > \*Originally posted by scr4 \* > \*\*I hate having to use my background to back up my statements but since you ask, I _am_ an astronomer. I may not have a Ph.D quite yet but I make a living as an astronomy researcher. \*\* …And…? ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [August 30, 2003, 5:27am UTC](https://boards.straightdope.com/t/derivation-of-color-from-light/198480/34 "2003-08-30T05:27:17Z")
…and I do think color is actually an inherent property of EM radiation. (I thought that was obvious from my previous post?) ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [August 30, 2003, 5:29am UTC](https://boards.straightdope.com/t/derivation-of-color-from-light/198480/35 "2003-08-30T05:29:47Z")
…And… I think you’re embarassing yourself, **Q.E.D.** ---
**Author:** ![Joe\_Random](https://avatars.discourse-cdn.com/v4/letter/j/e8c25b/32.png) [@Joe\_Random](https://boards.straightdope.com/u/Joe_Random)\ **Post date:** [August 30, 2003, 5:31am UTC](https://boards.straightdope.com/t/derivation-of-color-from-light/198480/36 "2003-08-30T05:31:48Z")
To say that color is a property of light is akin to saying that pain is a property of fire. Fire can induce the _experience_ of pain in humans. Likewise, light can induce the _experience_ of color. The intensity of the pain correlates with the heat of the fire. Likewise, the hue of the color correlates with the wavelength of light. However, color is not an intrensic property of light anymore than pain is an intrensic property of fire. It’s just a perception that happens to _map to_ an intrensic property. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [August 30, 2003, 5:33am UTC](https://boards.straightdope.com/t/derivation-of-color-from-light/198480/37 "2003-08-30T05:33:22Z")
Well, it isn’t. Wavelength is. Frequency is. Color isn’t. You can say that a given wavelength of light corresponds to a given color _only_ because you’ve perceived that color _with your brain_. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [August 30, 2003, 5:36am UTC](https://boards.straightdope.com/t/derivation-of-color-from-light/198480/38 "2003-08-30T05:36:49Z")
> [@](#): > > \*Originally posted by Joe Random \* > \*\*To say that color is a property of light is akin to saying that pain is a property of fire. Fire can induce the _experience_ of pain in humans. \*\* Thank you, **Joe**. At least someone understands the point I am making here. **Desmostylus** , how exactly an I embarassing myself? ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [August 30, 2003, 5:38am UTC](https://boards.straightdope.com/t/derivation-of-color-from-light/198480/39 "2003-08-30T05:38:05Z")
Read the dictionary definition again. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [August 30, 2003, 5:41am UTC](https://boards.straightdope.com/t/derivation-of-color-from-light/198480/40 "2003-08-30T05:41:20Z")
> [@](#): > > \*Originally posted by Desmostylus \* > \*\*Read the dictionary definition again. \*\* Right, cause we all know dictionary defintions are soooooo scientifically accurate. Try again. [Previous page](https://boards.straightdope.com/t/derivation-of-color-from-light/198480.md?page=1) [Next page](https://boards.straightdope.com/t/derivation-of-color-from-light/198480.md?page=3)